Eight radiators, disposed along a line, are coupled to a radar via a Butler matrix. In response to a transmitted signal from the radar, inverse transform signals that have amplitudes representative of values of a sinusoid in an angular range of zero radians to .pi. radians is applied to the Butler matrix....http://www.google.com/patents/US4163974?utm_source=gb-gplus-sharePatent US4163974 - Antenna feed system
